I've noticed that when I use the image uploader, the URL to the image ends up looking like this:
http://example.com/files/2008/07/example.jpg
Obviously this isn't a real directory - and the true URL is:
http://example.com/wp-content/blogs.dir/1/files/2008/07/example.jpg
However I use a theme where I have to copy and paste the URL of the image into a custom field for thumbnail creation. Putting the virtual URL doesn't work - but using the actual URL does work.
Is there a way to set up WPMU to just use the actual URL when it displays in your site?